The following is a list of the most pertinent prior art disclosures known to the inventor at the time of the filing of this application:
______________________________________ U.S. PAT. NOS. ______________________________________ 1,081,536 Jeppson Dec. 16, 1913 1,251,888 Horn Jan. 1, 1918 1,442,413 Olsson Jan. 16, 1923 1,893,313 Willetts Jan. 3, 1933 3,197,315 Jacobs et al July 27, 1965 3,303,034 Troell et al Feb. 7, 1967 4,090,881 Keel et al May 23, 1978 4,222,782 Alliegro et al Sept. 16, 1980 4,244,745 Havranek et al Jan. 13, 1981 ______________________________________
The Jeppson patent contains an early disclosure of a cement that includes a predominant amount of a fused crushed alumina grain for bonding aluminous bricks. The mix is in the proportions of 85 to 95 parts of the alumina grain together with a suitable bonding material in the form of a neutral clay or acid plastic clay or lime or magnesia adapted to be mixed with water and fired in place to provide a cement that does not react with the aluminous bricks.
Horn describes an alumina and clay mixture adapted to be cast or molded for making ceramic objects. He provides a mixture that is "high in alumina" to which is added a ground mix of burnt clay and lean clay, for example shale. Molded and fired objects made with this mix are described as being able to withstand exposure to temperature changes, are long wearing, have a high degree of impermeability, and have high strength. It is suggested that ceramic heating elements and other bodies may be made by casting or compression molding and firing without undue distortion, to produce articles that are well adapted to withstand internal and external pressures.
There is no disclosure suggesting a use of this Horn mixture as a cement for bricks.
Olsson describes a mix of essentially 95% alumina and 5% bentonite having refractory properties adapted to serve as a liner for furnaces and crucibles. It is alleged that the 5% of bentonite is sufficient clay to serve as a binder while rendering the mix plastic as it is being worked to produce a lining that contained a higher percentage of refractory material than was then theretofore known.
Willetts teaches the art how to make a fired refractory brick having a superior resistance to shrinkage and spalling in use. He proposes a mixture of white bauxite, Georgia Klondike white kaolin and a hard bauxitic fire clay which is a reactive mix that upon being fired produces a mullite with a glassy matrix that has a high point of fusion. The mix described may be molded and fired to produce bricks or refractory blocks that are resistant to deformation, slagging and spalling when in use.
Jacobs et al discloses a gunning mix adapted to be wetted and rammed into place to be fired. The mix includes alumina and clay together with wetting and lubricating components that enable the mix to be readily wetted and placed when the lining is to be installed. This mixture has high green strength upon being dried and can then be fired to allegedly have excellent high strength characteristics as a monolithic surface structure that is free of joints such as ordinarily found in brick lined furnaces.
Troell et al also describes a ramming cement mix making use of alumina and a bentonite clay mix together with a phosphoric acid component. It is stated that the bentonite and phosphoric acid are not reactive in the dry mix but the mix may be easily rendered plastic by the addition of water to enable the wetted mix to be placed as a liner in a furnace for example, to be fired in situ to provide a monolithic wall structure.
Keel et al teach the art of how to make a refractory adhesive that contains a large proportion of mullite mixed with ceramic fibers, colloidal silica, alumina and bentonite. The resulting mix, when fired acts as an electrically insulating binder that has refractory properties.
Alliegro et al describes another type of raw batch for a refractory mix adapted to be rammed or gunned into place to form a monolithic liner in a furnace or the like. He describes a basic selection of grain sizes for the essential refractory component together with sintering aids and fluxes designed to produce a fired wall having a minimum degree of porosity.
Havranek et al also shows a reactive gunning mix for producing monolithic furnace liners wherein a refractory dry mix containing a calcium aluminate cement is one component that is mixed with a second silica sol component and water when the cement is being prepared for placement. Reactive alumina is included in the dry mix portion and apparently combines with the silica when the monolithic wall is fired while the water content required by the calcium aluminate cement can be reduced by reason of the addition of the silica sol in order to increase the green strength of the cement during placement in the wall.